Methods used for the I-35 Bridge Collapse and the Bonner Bridge and Queen Isabella Bridge Investigations

Transcription

1 Failure Investigation and Structural Assessment Strategies: Methods used for the I-35 Bridge Collapse and the Bonner Bridge and Queen Isabella Bridge Investigations 1

2 Outline and Objectives Introduction Forensic Evaluations Failure, defined d Investigation of Material Failure Bonner Bridge Causeway Queen Isabella Causeway Investigation of Structural Failure I-35 Bridge Collapse

3 Forensic Evaluation Field Investigations Condition Assessment Service Life Prediction

4 Forensic Evaluation Field Investigations Condition Assessment What will fail first? Service Life Prediction

5 What constitutes Failure?

6 Failure, defined Failure An unacceptable difference between expected and observed performance - (ASCE Technical Council on Forensic Engineering ) Overstresses Large deflections Wide concrete cracks Fatigue cracking

7 Failure, defined Collapse Gross movement of major members or a significant portion of the structural system that renders them incapable of supporting the intended loading. Failure does not imply collapse, but collapse is viewed as a structural failure.

8 What Qualifies as a Failure? Catastrophic structural collapse

9 What Qualifies as a Failure? Catastrophic structural collapse

10 What Qualifies as a Failure? Catastrophic structural collapse

11 What Qualifies as a Failure? Catastrophic structural collapse?

12 What Qualifies as a Failure? Material Failure?

13 What Qualifies as a Failure? Material Failure?

14 What Qualifies as a Failure? Material Failure?

15 What Qualifies as a Failure? Material Failure?

16 Investigating g Bridge Failures

17 Bridge Structure Investigations The Forensic Team Field Engineers Field Technicians Material Scientists The Equipment Super-duper extra-special widget Primary Tools Visual Inspection Materials Testing Advanced Equipment

18 Bridge Structure Investigations Visual Methods (simple) Close-up Visual Inspection Sounding Crack Mapping Cover Meter

19 Visual Inspection Close-up Crack widths

20 Sounding Detecting unsound and deteriorated areas of concrete Hammer-tapping to locate boundary of unsound concrete Low tech

21 Visual Inspection Close-up Hands-on Concrete condition Rebar condition

22 Visual Inspection Close-up Carbonation Testing Young crack Old crack

23 Bridge Structure Investigations Non-Destructive Evaluation (advanced) Half-Cell Potential Linear Polarization Ultrasonic Pulse Velocity Dye Penetrant Testing Magnetic Particle Testing Material Sampling Concrete Petrography Steel Composition

24 Bridge Structure Investigations Applying what we know to Investigating Causeway Bridge Structures Local Examples Martin Point Bridge over the Presumpscot River Built 1943, is 1,400 feet Veterans Memorial Bridge over the Danvers River Built 1997, is 1,710 feet Larger Structures Bonner Bridge over Oregon Inlet, North Carolina Built 1964, is approximately 2.4 miles long Queen Isabella Memorial Causeway, south Texas Built 1974, is approximately 2.5 miles long

25 Bridge Structure Investigations The need for Investigation Bonner Bridge Routine Investigation Known Material Problems Evaluation of Past Repairs Service Life Queen Isabella Causeway Routine Investigation Evaluation of existing corrosion mitigation systems Evaluation of Past Repairs Service Life

26 Bonner Bridge, North Carolina - Completed April Approximately 4 years to complete - Total Length = 2.4 miles Spans - Superstructure t Precast Girders and Structural Steel - Substructure Cast-in-place concrete

27 Bonner Bridge, North Carolina

28 Bonner Bridge, North Carolina

29 Bonner Bridge, North Carolina

30 Bonner Bridge, North Carolina

31 Focus of Investigation Evaluate Construction materials On-site Concrete production Remote location Evaluate performance of repairs Evaluate corrosion mitigation program 1986 Implementation Discreet anode cathodic protection systems Pile caps, splash zone regions

32 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

33 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

34 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

35 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

36 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

37 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

38 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

39 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

40 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

41 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

42 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

43 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

44 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

45 Bonner Bridge, North Carolina Field Investigation Access Inspection Visual NDE Concrete Samples

46 Bonner Bridge, North Carolina Concrete Petrography Girders Pile Caps Bridge Deck

47 Bonner Bridge, North Carolina Concrete Petrography Girders Pile Caps Bridge Deck

48 Bonner Bridge, North Carolina Concrete Petrography Girders Pile Caps Bridge Deck 0.1 in.

49 Bonner Bridge, North Carolina Concrete Petrography Girders Pile Caps Bridge Deck

50 Bonner Bridge, North Carolina Concrete Petrography Girders Pile Caps Bridge Deck

51 Summary of Findings Evaluate Construction materials Poor concrete quality Coral used in original concrete Evaluate performance of repairs Concrete repairs did not perform well Cathodic Protection Not maintained Non-functional

52 Queen Isabella Causeway - Connects Port Isabel to South Padre Island, TX - Completed April Approximately 2 years to complete - Total Length = 2.5 miles Spans - Superstructure Precast Girders and Structural Steel - Substructure Cast-in-place concrete

53 Queen Isabella Causeway - Connects Port Isabel to South Padre Island, TX - Completed April Approximately 2 years to complete - Total Length = 2.5 miles Spans - Superstructure Precast Girders and Structural Steel - Substructure Cast-in-place concrete

54 Queen Isabella Causeway - Connects Port Isabel to South Padre Island, TX - Completed April Approximately 2 years to complete - Total Length = 2.5 miles Spans - Superstructure Precast Girders and Structural Steel - Substructure Cast-in-place concrete

55 Queen Isabella Causeway Evaluate construction materials On-site concrete production Remote location Evaluate performance of repairs Evaluate corrosion mitigation program 2003 Implementation Thermally sprayed cathodic protection systems Pile caps, splash zone regions

56 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples

57 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples

58 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples

59 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples

60 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples

61 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples

62 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples: - Assist NDE

63 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples: - Assist NDE

64 Queen Isabella Causeway Field Investigation Access Inspection Visual NDE Concrete Samples: - Assist NDE

65 Queen Isabella Causeway Lab Investigation Access Inspection Visual NDE Concrete Samples: - for petrography

66 Queen Isabella Causeway Lab Investigation Access Inspection Visual NDE Concrete Samples: - for petrography

67 Queen Isabella Causeway Lab Investigation Access Inspection Visual NDE Concrete Samples: - for petrography

68 Queen Isabella Causeway Lab Investigation Access Inspection Visual NDE Concrete Samples: - for petrography

69 Queen Isabella Causeway Lab Investigation Access Inspection Visual NDE Concrete Samples: - for petrography

70 Conclusions Material Performance Composition Location within structure Maintenance & Protection Service Life Extensions

71 Conclusions Material Performance Composition Location within structure Maintenance & Protection Service Life Extensions

72 Conclusions Material Performance Composition Location within structure Maintenance & Protection Service Life Extensions

73 Conclusions Material Performance Composition Location within structure Maintenance & Protection Service Life Extensions Det terioration Expected Service Life of Structure Time (years)

74 Bonner Bridge vs. Queen Isabella Bridge

75 Investigation of the I-35W Bridge Collapse Mark R. Chauvin Wiss, Janney, Elstner Associates, Inc.

76 Outline Description of Bridge Deck Truss Brief History Collapse Field Work Recovery and Removal Observations Structural Analysis Conclusions

77 Description of Bridge 77

78 Description of Bridge Interstate 35 is a major N-S route thru MN Divided into parallel arterials thru metro 35E through h St. Paul 35W through Minneapolis I-35W crosses Mississippi River adjacent to U of MN campus, just NE of downtown 2004 ADT =141,000 vehicles (5640 trucks) 78

79 OVERALL Area Picture 79

80 Description of Bridge (cont.) Designed in 1965 by Sverdrup & Parcel Opened to local traffic in 1967 Eight 12 ft. wide lanes 3 traffic + 1 acceleration/deceleration N + S General construction: 6-1/2 inch thick reinforced concrete deck Two 3-span continuous deck trusses Eleven approach spans (5 south, 6 north) Total bridge length = 1907 feet 80

81 Deck Truss Two parallel steel trusses: Welded box-shaped top and bottom chords 21 inches wide x 28 inches deep (typ.) Welded box-shaped vert. + diag. C members H-shaped vert. and diag. T members Connected at nodes with 1/2, 5/8, 3/4 and 1 inch thick steel gusset plates (50 ksi) 7/8 inch diameter rivets 81

82 South Half of Deck Truss ROLLER ROLLER North Half of Deck Truss FIXED ROLLER WJE/MnDOT Nomenclature: Top chord nodes U#, bottom chord nodes L# Nodes 0 (south end) to 14 (midspan) Nodes 13 to 0 (north end) 82

83 Deck Truss (cont.) CROSS-SECTION AT PIER 7 83

84 84

85 N Pier 6 Pier 7 85

86 Brief History 86

87 History - Work 1977: Concrete overlay increased deck thickness from 6-1/2 inches to 8-1/2 inches 1998/1999: New median and outside barrier Fatigue retrofits of approach girders Deck de-icing system Painting 87

88 History - Work (cont.) Progressive Contractors Inc. (PCI) Patching and overlay work began June 2007 Removal and replacement of 2 inch 1977 overlay Rotomilling outer 2 NB/SB lanes first Aggregate and sand stockpiled near mix equipment beyond end of each placement. Seven placements complete by August 1 Preparation for 8 th placement underway 2 inside southbound lanes Nodes 0 to 14 88

89 July 18, 2007 (looking southbound) 89

90 90

91 577 kips total * 48 kips 73 kips 184 kips gravel 199 kips sand 51 kips * Note: about 2 of deck had been removed ed from the southbound construction lanes 91

92 N Sand Gravel Mid-afternoon on day of collapse 92

93 Collapse 93

94 N 94

95 N 95

96 N N 96

97 U S COE Security Camera U.S. COE Security Camera (looking north) L11

98 U.S. COE Security Camera L11

99 U.S. COE Security Camera L11

100 South end clearly enters river first U.S. COE Security Camera

101 Collapse Occurred at 6:05pm on August 1 st, 2007 Temperature: 92.1 F Peak of 92.9 F at 4:30pm Light to moderate winds 10 to 18 mph 4 of 8 lanes closed to traffic for PCI work Approx. 110 vehicles on bridge Including construction materials and equipment 13 fatalities, 145 people injured 101

102 Field Work 102

103 Field Work NTSB lead federal investigative agency WJE retained by MnDOT on Aug. 3rd Field tasks included: Post-collapse documentation Member identification, marking and tracking Demolition assistance Monitoring recovery and removal operations Material sampling 103

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109 Field Work Summary of Observations River span essentially dropped straight down into river, very little twist or rotation Primary failure regions on north and south ends of submerged section were symmetric Essentially intact between 12 and 10 Similar failure modes at all four U10 nodes Gussets separated into multiple sections No evidence of collapse initiation at other locations 109

110 N 110

111 N

112 N 112

113 U10-U11 U11 U9-U10 L9-U10 U10-L10 U10 Node U10-L11

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124 Structural Analysis 124

125 Structural Analysis Loads at time of collapse: Self-weight Construction materials and equipment: Located in SW quadrant of river span Placed on bridge 2-3 hours prior to collapse Vehicle traffic in 4 open lanes Findings: Forces in most severely loaded deck truss members nearly equal to design service loads 125

126 Most critically loaded main truss member was L9W- U10W; at 102% of the original design service load on 8/1/07 U10 W L9 W

127 Node U8 U10 Node Design Detail 127

128 U10 Node; plane of known horizontal shear

129 Simple Initial Calculation Check shear only Ignore the normal stresses which also exist at this plane Assume shear uniformly distributed along entire plane Assume loading is equal to original design dead d load x (1977 overlay) No traffic or construction load considered

130 Initial Calculation Results Sum of horizontal forces in web elements (and in chords) = 2343 k Plate gross area = 104 sq. in. Avg. shear stress = 2343/104 = 23 ksi Allowable (1964 AASHO) = 15 ksi Yield 0.6 x Fy = 30 ksi Close

131 U10 Node section equilibrium check at yield

132 Section for L9-U10 -Shear and normal forces acting together th -Magnitude governed by Von Mises yield criteria along entire section -Internal forces in equilibrium with external forces for each section -Loading proportional to dead load distribution U10 Node section equilibrium check at yield

133 Initial Analysis (cont.) Maximum sustainable compression load in L9-U10 = 2300 kips at measured steel yield strength (51 ksi) Estimated load in L9 - U10 at time of collapse (including all loads) = 2340 kips Avg. shear stress along horizontal plane = 28 ksi L11 gusset also found to be undersized (1/2 inch)

134 U10 Finite Element Analysis Analysis of Node U10 and associated members Apply loading proportionally as indicated in finite element model of entire structure Steel properties determined from testing Material and geometric nonlinearities Initial plate distortion evaluated 2003 URS photos

135

136 L9-U10 -Light green corresponds to Von Mises yield level stress -Strain hardening only in small areas near top of L9-U10 and around lowest row of chord rivets (circle) -Ultimate strength 2470 kips with flat plates -Ultimate strength 2390 kips with initial plate edge distortion similar to that observed in pre-collapse photos

137 Conclusions 137

138 Conclusions Construction of deck truss was consistent with design documents As-built capacity of U10/10 and L11/11 gusset plates roughly half of capacity that required by governing design code These plates had not experienced significant damage or deterioration prior to collapse U10 gusset plates were the most critically loaded elements in the deck truss on 8/1/07 138

139 Conclusions (cont.) Bridge collapse initiated by failure of the improperly designed U10 gusset plates As-built ultimate capacity of U10 in vicinity of L9-U10 compression diagonal essentially identical to demands at time of collapse Failure mode of U10 gusset predicted by nonlinear FEM consistent with the condition of the actual plates after collapse U10 became unstable when L9-U10 loading created yield mechanism in gussets 139